Motor starting and safety switch



Jan. 16, 1951 A. R. LUCAS MOTOR STARTING AND SAFETY SWITCH Original Filed Sept. 28, 1946 IIIIIIIIIIIIIIIIII lll'lll INVENTOR. A/frea A. Lucas n n I w Reissuetl Jan. 16, 1951 MOTOR STARTING AND SAFETY SWITCH Alfred B. Lucas, Gallon, Ohio Original No. 2,475,038, dated July 5, 1949, Serial No. 700,074, September 28, 1946. Application for reissue May 24, 1950, Serial No. 163,980

'7 Claims.

Matter enclosed in heavy brackets appears in the original patent but forms no part of this reissue specification; matter printed in italics indicates the additions made by reissue The present invention relates to electric switches and more specifically to switches through which current is supplied to motors first to the starting windings and then the running windings.

Among the objects of the invention is a switch provided with means for dividing the initial current between the two motor windings and subsequently breaking the circuit through the starting winding. 7

Another object is a switch provided with means for breaking the motor circuit under conditions of overload or excessive heating.

Still another object is a switch which automatically restarts the motor when the objectionable condition has been relieved.

Other objects and advantages will readily occur to those skilled in the art upon reference to the following description and the accompanying drawings in which Fig. l is a top plan view of the switch elements.

Fig. 2 is a side view thereof and also shows diagrammatically the motor connections.

Fig. 3 is a view similar to Fig. 2 but shows in addition, diagrammatically, means for controlling the timing of the re-start.

Fig. 4 is a fragmentary section showing the switch of Fig. 3 in open position.

As shown in the drawing, the switch consists of a base or housing ll] of insulating material relatively long and having at one end anchorage means II for a pair of spring arms I2, one on each side of but not in contact with, an arm [3 the cross member I2A, i a curved flat spring member 20, this being reversely curved at its ends to form sockets and being made of light spring of bi-metal, which extends through and projects from the endwall of the member I0, the projectingend serving as connecting means for a lead wire M.

The free end of arm I3 carries a contact I3A exposed on both upper and lower faces of the arm, while the arm itself is considerably shorter than the spring arms l2. The spring arms l2 are fixed at their free ends to a conducting cross member HA which carries a contact I2B exposed on both upper and lower faces of the member l2A.

Located in the end of the base 10 is a short conductor it the inner end of which carries a contact liiA in position to coact with the contact HE and to the outer end of which is connected a lead wire 16.

In the bottom of the base In is another fixed contact l'l mounted on a conductor I'IA leading from the base or housing and to which is con- :nected a lead wire Hi. This contact I! is below and in position to coact with the contact ISA carried by the bi-metal arm l3. The housing I0 lines in Fig. 2.

material. Also extending between the parts is a-flexible lead wire 2|.

In the use of the switch described above, the lead wire I6 is connected to one end of the running winding A of a motor while the other end of Winding Ais connected to one end of the starting winding and at their junction they are connected to a power supply or return line C. The conductor I4 is directly connected to or is a part of the other power lead D. The conductor l8 leads to the other end, or end opposite the running winding, of the starting winding B.

When the power leads C and D are not energized and no current is flowing through the switch, the parts are in the position shown in full When the current is turned on, the flow from lead C will be to the bi-metal arm [3 and from this it will be divided and part will go to contact I! and part through member 20 and flexible lead'2l to contact 15A, so that from lead D the flow of current will be through both the starting winding B and running winding A, all of the current traversing the bi-metal arm i3.

As a consequence, the arm 13 will be heated rather quickly and the contact of HA with I? will soon be broken. 'The time, of course, may

same

readily be pre-set by using the proper strip for arm [3.

With separation of contacts [3A and 11, current flow will continue through contacts I2B, [5A, lead l6 and windings A. The heating effect on arm l3 will be at the same time reduced, so that, under usual running conditions, the arm l3 will not move up sufliciently to break the running circuit.

When, however, an overload occurs, and with it an excessive current flow, the arm I3 will move further and cause the toggle spring 20 to snap over center and separate contacts I2B and IEA, as indicated in Fig. 4, and this condition will continue until arm 13 cools sufiiciently to move down and cause the toggle spring 20 to again thrust the latter contacts together.

While it may not be necessary in most cases to delay the re-start for a greater time than that of the natural cooling of arm Hi, this time may be [prolounged] prolonged by such means as is shown in Fig. 3. In this figure, the stops [0A and IOB are shown as contacts NBA and HUB connected respectively to leads III and H2, the former leading to a variable resistance device [I IA] 111A and the latter to any suitable device DD for utilizing the current. This arrangement provides for continuing the current flow through arm l3 when the parts are in the position of Fig. 4 and so continues the heating of the arm. It is of course to be understood that the current flow through leads Ill and H2 will be so regulated that the arm l3 will be allowed to cool at such rate as will produce the time lag desired.

I claim:

1. A motor starting and safety switch consisting of a suitable [enlongated] elongated. base having adjacent one end thereof a stationary contact adapted to be connected to the running windings of a motor and a second stationary contact adapted to be connectedto the starting windings of said motor, a spring arm fixed to the other end of said base and carrying a contact at its free end, adapted to co-act with the first mentioned stationary contact to complete the running circuit, a second arm. fixed to said other end of said base and carrying at its free end a contact adapted to co-act with the second stationary contact to complete the starting circuit through said motor, said second arm being connected to a source of current supply and being of bi-metal adapted to flex when heated, said second arm when unheated having its contact in circuit closing relation with the second stationary contact, a fiexible conductor fixed to said bi-metal arm and to the contact carried by said spring arm, and a spring toggle member between said bi-metal arm and said spring arm and adapted to move said spring arm and contact away from. its co-acting stationary contact when the bi-metal is unduly flexed due to excessive heating.

[2. A motor starting and safety switch consisting of a base member, a spring arm fixed thereto and carrying a contact at its free end, a fixed contact normally touching the first contact, a second conducting arm adapted to fiex when heated fixed to said base and arranged in generally parallel relation to the spring arm said second arm having a. contact adjacent its free end, a fixed contact which the contact on said second arm touches when cold, a toggle spring cooperating with the free ends of said arms and arranged to press together the contact on said spring arm and its cooperating fixed contact when said second arm is subjected to normal heating and normal flexing and to separate the spring arm contact and its fixed contact when the second arm is subjected to abnormal heating and thereby abnormal flexing] e [3. An electric switch consisting of an elongated base having fixed at one end thereof a spring arm and abi-metallic conducting arm generally parallel therewith, means for connecting said bimetallic arm to a current source, a contact fixed t the free end of each arm, a pair of stationary contacts fixed to said base and adapted to co-act with respective arm carried contacts, and to. lie in circuit closing position when cold, said bi-metal arm adapted to fiex when heated bypassage of current therethrough and thereby separate its contact from its co-acting fixed contact, and a spring toggle ember acting between said bimetal arm and said spring arm and adapted to separate the spring arm carried contact from its co-acting fixed contact when through excessive heating said bi-metal arm is unduly flexed] 4. A motor control [electric] switch consisting of an elongated base having fixed at one end a contact swung by one ting out the thereof a spring arm and a bi-metallic conducting arm generally parallel therewith, means for connecting said bi-metallic arm to a current source, a contact fixed to the free end of each arm, a pair of stationary contacts fixed to said base and adapted to co-act with respective armcarried contacts in circuit closing position when said bi-metal arm is cold, means for connecting the fixed contact co-acting with the spring arm carried contact to the motor, said bi-metal arm. adapted to flex when heated by passage of current therethrough and thereby separate its contact from its co-acting fixed contact, a spring toggle member acting between said arms to maintain under normal heating the circuit closed relation of the contact on said spring arm and its co-acting fixed contact and to separate the latter under abnormal heating, a second pair of fixed contacts with which the arm carried contacts are adapted to co-act when said arm has been moved due to excessive heating, at least one of said second pair of fixed contacts being connected in a circuit other than the motor circuit and to thereby increase the cooling time for said bime-tal arm.

5. A self acting switch for automatically cutting out the starting circuit shortly after an electric motor starts and cutting out both circuits or the running circuit during overload, having in combination spring and thermally sensitive arms fixedly supported each at one end, a spring toggle connecting the other ends of said rms, a pair of swinging contacts supported oneon the end of one armand the other on the end of the other am where the arms are connected by the said spring toggle, a,- pair of fixed contacts one opposite and cooperating with each swinging contact, the one set (one movable and one fixed) of contacts arranged to be in circuit with the starting winding of the motor and the other set arranged to be in circuit with the running winding when the arms are not overheated, the thermally sensitive arm being at one time in circuit with the starting winding and the running winding, and after starting, being in circuit only with the running winding and having two states of distortion under heat developed by the passage of current through said arm, one a distortion that separates the contacts controlling the. starting winding shortly after motor starting and a second state of distortion wherein the set of contacts that control the running circuit are also separated to stop the motor during overload.

6., A self-acting switch for automatically cutsturting circuit after starting and for cutting out both circuits or the running circuit of an electric motor during overload, said switch having in combination a, base of electric-insulating material, a thermally sensitive arm supported at one end on said base and free to distort at the char end under influence of the heat generated by passage of current and. passing current at all times through th same conductor length and path on said arm, said thermally sensitive member distortuble at its free end and movable less than its complete capacity under the combined normal starting and running loads, spring arm means including at least one arm fixedly sup.- ported at one end of said housing and free to swing at the other end, spring toggle. means connectz'ng the freeends of the thermally sensitive and the spring arms, a pair of contacts, one a fixed one on the base for electrical connection with the starting winding of the motor, the other of said arms and furnished with current through the full conductor length of said distortable thermally sensitive member, a second pair of contacts one a contact fixed to said base and having a lead for connection with the running winding of the same motor, the other a contact associated with an arm, the thermally sensitive arm operating under the heat generated after a given time by the normal starting and running current to cause a partial distortion to separate the first pair of contacts only and cut out the current to the starting winding lead and operating under excessive load to distort to its limit thereby separating all contacts and breaking the leads to both windings, all arms automatic lly returning on cooling to normal service positions.

7. The combination claimed in claim 6 in which the thermally sensitive arm is a bimetallic arm which swings at its free end under heat changes due to the passage of current or cessation of passage of current.

8. Th combination claimed in claim 6 in which 6 the arms and spring toggle throw over center with the full distortion of the thermally sensitive arm.

9. The combination claimed in claim- 6 in which 5 the spring toggle includes a U spring strip.

ALFRED R. LUCAS.

REFERENCES CITED The following references are of record in the 10 file of this patent or the original patent;

UNITED STATES PATENTS Number Name Date 1,905,823 Dybvig Apr. 25, 1933 15 2,068,374 Carlson Jan. 19, 1937 2,237,705 Kohl Apr. 8, 1941 2,378,784 Obszarny June 19, 1945 2,414,778 Tratsch Jan. 21, 1947 2,417,912 Clark Mar. 25, 1947 :0 2,505,689 Rickmeyer Apr. 25, 1950 

